Understanding EC2 Dedicated Hosts and Dedicated Instances

Introduction

Understanding Amazon EC2 Dedicated Hosts and Dedicated Instances can be essential for businesses with specific compliance, regulatory, or software licensing needs. Here's an easy-to-understand overview:

EC2 Dedicated Hosts

1. What They Are: EC2 Dedicated Hosts are physical servers entirely dedicated to your use. They offer the capacity to run EC2 instances in an isolated environment, meeting stringent compliance and regulatory requirements.

2. Compliance and Licensing: These hosts are particularly useful for adhering to specific compliance needs and for utilizing existing server-bound software licenses. These licenses might be based on several metrics such as per-socket, per-core, or per-VM.

3. Purchasing Options: There are several purchasing options for EC2 Dedicated Hosts:

   • On-Demand: You pay for the Dedicated Host on a per-second basis.
   • Reserved: This option comes with a commitment of 1 or 3 years and offers several payment modes - No Upfront, Partial Upfront, or All Upfront.

4. Cost Consideration: Dedicated Hosts are generally the most expensive option among EC2 offerings. However, they can be cost-effective for specific use cases, especially when dealing with complex software licensing (like Bring Your Own License - BYOL).

5. Visibility and Control: You have the visibility and control over how your instances are placed on these physical servers, which is crucial for meeting certain regulatory and compliance requirements.

6. Integration with AWS License Manager: This integration helps in managing software licenses, including those for Microsoft Windows Server and SQL Server.

7. Limitations: Note that RDS instances are not supported on Dedicated Hosts, and they cannot be launched in placement groups.

EC2 Dedicated Instances

1. How They Differ from Dedicated Hosts: While Dedicated Instances also run on hardware dedicated to a single customer, they may share this hardware with other instances in the same account.

2. Instance Placement: You don't have control over the exact placement of instances. However, after stopping and starting an instance, it can move to different hardware.

3. Launching Dedicated Instances: These can be launched in a Virtual Private Cloud (VPC) with dedicated instance tenancy. When you create a VPC, you have the option to specify its instance tenancy as 'dedicated', ensuring that any instance launched into this VPC is a Dedicated Instance.

4. Tenancy Modifications: You can change the tenancy of a stopped instance after launch, and the changes will take effect the next time the instance starts. However, for T3 instances, specific tenancy limitations apply, such as not being able to change the tenancy from 'host' to 'dedicated' or 'default'.

5. Flexibility: Dedicated Instances provide a flexible solution for those who require dedicated hardware but do not need the full control over instance placement that Dedicated Hosts offer.

Conclusion

In summary, EC2 Dedicated Hosts and Dedicated Instances offer solutions tailored to specific business needs related to compliance, licensing, and regulatory requirements. The choice between the two depends on the level of control and isolation you need, as well as your budget constraints.